Questions and Answers
What is the phenomenon called when electrons are ejected from certain metals by light exposure?
What is the effect of photon energy on the kinetic energy of the ejected electrons?
What happens when light of a frequency below the threshold frequency is applied to potassium metal?
How does the number of electrons ejected relate to the intensity of the light used?
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What is the threshold frequency for potassium metal?
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What occurs when red light shines on potassium metal?
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What relationship exists between the frequency of light used and the kinetic energy of the ejected electrons?
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Which of the following could be a reason why the photoelectric effect occurs at certain frequencies?
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How does the brightness of light affect the photoelectric effect?
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What is the key feature of how photons interact with electrons during the photoelectric effect?
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Study Notes
Photoelectric Effect Overview
- Discovered by H. Hertz in 1887; observed ejection of electrons when metals (e.g., potassium, rubidium, caesium) are illuminated by light.
- The process involves the absorption of energy by electrons from incoming photons, leading to their ejection from the metal surface.
Key Mechanics
- Sufficiently energetic photons transfer energy to electrons instantaneously during collisions, resulting in immediate ejection.
- Higher photon energy correlates with greater kinetic energy of the ejected electrons.
Experimental Observations
- Electrons are emitted as soon as light strikes the metal surface, indicating an immediate response.
- The quantity of ejected electrons is directly proportional to the light's intensity or brightness.
- Each metal has a specific threshold frequency (ν₀); below this frequency, no ejection of electrons occurs.
Threshold Frequency
- For potassium, the threshold frequency (ν₀) is 5.0 × 10¹⁴ Hz.
- Frequencies greater than ν₀ lead to ejection of electrons with increasing kinetic energy as frequency increases.
Comparison of Light Frequencies
- Red light (ν = 4.3 to 4.6 × 10¹⁴ Hz) does not cause ejection of electrons, regardless of intensity; no photoelectric effect occurs.
- Yellow light (ν = 5.1 to 5.2 × 10¹⁴ Hz), even at low intensity, successfully induces the photoelectric effect in potassium.
Summary of Relationships
- Ejected electron count varies with light intensity; however, their kinetic energy depends solely on the light frequency, not intensity.
- Internal atomic interactions dictate the threshold frequency specific to each metal, critical for observing the photoelectric effect.
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Description
Explore the fascinating phenomenon of the photoelectric effect as demonstrated by H. Hertz in 1887. This quiz will test your understanding of how light can eject electrons from certain metals and the principles behind this important discovery in physics. Be prepared to delve into the concepts of photons, energy transfer, and electron behavior.
